AU101 Sansui amp schematic please

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  • zen
    Badcaps Veteran
    • Apr 2011
    • 511
    #1

    AU101 Sansui amp schematic please

    Hi all

    Right channel works but a touch noisy .

    Left channel no audio .

    Proved issue is on the control pre-amp board , by injection an audio signal directly into the audio output / drive board
    Attached Files
    Tags: None
    • zen
      Badcaps Veteran
      • Apr 2011
      • 511
      #2
      Re: AU101 Sansui amp schematic please

      Schematic really poor quality ,but managed to reverse engineer circuitry .

      TR701 , 2SC871 breaking down under load .

      Replaced with 2SC1345 , which i had to fit reversed due to pin configuration .
      Attached Files

        Comment

        • redwire
          Badcaps Legend
          • Dec 2010
          • 3910
          • Canada
          #3
          Re: AU101 Sansui amp schematic please

          I find many old grey Elna electrolytics pretty much dead nowadays, they dry out and go low value. I'd replace them all.
          You can compare DCV readings between channels. Two transistors are the phono preamp, leaving just one for the control preamp.
          2SC871 is 25V low noise and high beta min. 350 typ >400. Hand selected KSC1845's or 2SC2240BL's or BC549B or C (different pinout) and lately I am using the Zetex power parts popular for low noise audio use due to their large die, like ZTX690B. But they are hard to find lately.

          schematic is in the manual: https://cdn.badcaps-static.com/pdfs/...8679969d14.pdf

            Comment

            • zen
              Badcaps Veteran
              • Apr 2011
              • 511
              #4
              Re: AU101 Sansui amp schematic please

              Thanks Redwire , all the other electrolytic caps checked out good.

              TR701 was the issue , tested for several days & all working well .

                Comment

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